Actuating mechanism for gas operated firearms



Jan. 29, 1946. J. c. LGARAND ACTUATING MECHANISM FOR GAS OPERATED FIREARMS Filed June 5, 1942 2 Sheets-Sheet 1 tlnhn E- Garland %W-WW Ema wa Jab. 29, 1946. J. c. GARAND ,3 ,62

NG MECHANISM FOR GAS OPERATED l FIREARMS Filed June 5, 1942 2 Sheets-Sheet 2 3mm Lluhn E- E'ar'and Patented Jan. 29, 1946 ()FFICE ACTUATING-MECHANI-SM FOR GAS OPERATED FIREARMS John C. Garand, Springfield, Mass.

Application June 5, 1942, Serial No. 445,960

2 Claims. (01. 42-3) (Granted under the act of March 3, 1.883,,asamended April 30, 1928; 370.0. G. 757') The inventiondesoribedr' herein may be manufactured;,and used by or for theGovernment for.

governmental purposes, without the payment. to me. of. any royalty thereon.

This invention. relates to the. actuating member of agas operated firearm of the. automatic orssemi-automatio type.

Previous designsof gas operated firearms have.

utilized: actuating mechanisms consisting of a piston and. cylinder arrangement wherein the piston isnot rigidly connected to the breech operating mechanism but is adapted to impart a hammer-like blow tothe breech operating. mechanism, by: action of the gas pressure developed in the barrel after discharge of the cartridge.

Theforce imparted to the breech operatingrnechanism by such. blow must transfer suflicient kinetic energy to the breech operating mechanism to enable it: to perform the conventional operations generally necessary in a firearm of this type; namely, bolt unlocking, bolt retraction, cartridge extraction and ejection and compression of theoperating pring which then accomplishes cartridge loading, bolt closing and bolt locking. In such prior designs, there was always difliculty encounteredinsecuring prolonged operation of the firearm without cleaning due to theaccumul'ationof. carbon and other deleterious material deposited from the gas entering the actuating mechanism; Such deposit naturally produced a binding and'stickiness of'the piston and other defects which eventually impaired or prevented the proper operation of the firearm. Prior designs of actuating mechanisms had the further disadvantage in that the gas pressure was suddenly applied to the entire area of the piston. The resulting shock blow of course tended to produce a rapid deterioration and breakage of not-only the piston but also the related breech operating mechanism. Nor did'prior designs permit any convenient adjustment of the maximum gas pressure which was developed within the actuating mechanism. As a result, the actuating mechanism was only properly designed for one particular type of cartridge and the'performance ofthe actuating mechanism was greatly'affected, if not prevented, when it was desired to fire cartridges having different gas pressure developing properties.

It: is therefore an object of" this invention to provide an improvedactuating mechanism for a gasoperated firearm.

A: further object of. this invention is to provide; an 1 actuating: mechanism. wherein the ace cumulation. of; deleterious substance. deposited by the operating gases is substantially eliminated. through utilization of a gas blast for cleaning purposes. It is a further object of' this invention to provide an actuating mechanism utilizing. a gas blast for cleaning purposes wherein the gas blast is directed toward the muzzle end: of the firearm, and hence away from the operator;

It isia further object of this invention to provide an actuating mechanismfor a gas operated firearm in which the gas pressure force is applied to the actuator in steps.

It is a further object of this invention to pro-- vide an actuating mechanism for a gas operated firearm wherein the maximum gas pressure developed within the actuating mechanism maybe conveniently adjusted without disassembly of the actuating mechanism.

It is a further object of this invention to provide an actuating mechanism for a gas operated firearm which may be conveniently adjusted for optimum performance with all types of cartridges regardless of variation in their gas pressure developing properties.

The specific nature of the invention as Well as other objects and advantages thereof will clearly appear from a description of'a preferred embodiment as shown in the accompanying drawings in which:

Fig; 1 is a longitudinal sectional view of the improved actuating mechanism assembled on a firearm barrel and with the elements shown in this pre-firing position.

Fig. 2 is a view similar to Fig; 1 but showing the elements of the actuatingmechani'sm in their positions immediatel after firing.

Fig. 3 is a sectional view taken along the plane 33 of Fig; 1.

Fig. 4 is a sectional view taken along the plane 44 of Fig; 1.

Fig. 5 is a sectional view taken along the plane 5-5 of Fig. 1'.

Fig. 6 is a longitudinal sectional view, similar to Fig. l but showing a modification in the mounting of the piston.

Fig; 7 is an enlarged view taken along the plane 1-! of Fig. 6.

In Figure 1, the actuating mechanism A is shown in assembled relation to the barrel B of a gas operated firearm. The-actuating mechanism comprises a cylindrical supporting member I which snugly engages the barrel B in the vicinity of a gas port C provided in the barrel. It should be understood that the location of' the gasport is immaterial. to the practice of this invention audit. may bevaried .attwilldepending'. upon such.

At the rear end of supportingcylinder I, there is provided an integrally formed depending member 1 defining a bearing cylinder 6. A transverse hole 6a is provided in the common wall of the supporting cylinder I and bearing cylinder" 6. A

pin I is inserted in this hole and, by engaging a groove 8 in the barrel B, secures the supporting cylinder land its related parts to the barrel. A hollow nut 9 is screwed into the interior threads 6b provided on the end of bearing cylinder 6. This nut 9 is screwed into place prior to insertion of the pin I, and a groove So on the end of the nut is engaged by the pin I looking the nut in place.

Within the bracket 5, a piston member ID is inserted. This piston member is shaped somewhat like a bolt. The shank portion II of the piston fits tightly Within the cylindrical bracket 5 with the head portion IZ'abutting against the end of the bracket 5. This fit is sufficiently tight to maintain the position of the piston Ill but at the same time permits rotation of the piston shank II within the bracket 5 under the leverin action of a suitable tool inserted in a hole Ila in the extending end of the piston shank II The head I2 of the piston I5 lies outside of the bracket 5 in the space between the bracket 5 and the bearing cylinder 6. The head I2 hasa relatively narrow intermediate maximum diameter portion I'M. Between this cylindrical portion I2a and the top of the head I2, a sharply tapered surface I2!) is provided while between the maximum diameter portion I2a and the bot tom of the head l2, a slightly tapered surface I20 is provided. A circumferential groove I2d is provided in the shank I I immediately adjacent to the head I2 of the piston IE) to permit the grinding of the shank surface without production of a fillet at its juncture with the head I2.

An axial passage Illa is provided in the piston I running through the head I2 and extending well into the shank ii. Radial gas passages lib and Ho of substantially different diameters are provided in the shank II connecting with the passage Ifla. Each of these holes may be'aligned with the opening la in the supporting cylinders I by the forced rotation of the piston and thereby provides a direct passage for the gases leaving the barrel through the porthole C. While four or more holes of different diameters may be provided depending only upon the relation of the diameter of such holes to the circumference of the shank portion i I of the piston It, it has been found that two cf sueh holes IIb and lie will 1 generally sulTlce. The cross-sectional area ofthe hole He is approximately twice that of Nb. It is apparent that as the piston I8 is forcibly rotated within the bracket to successively align the holes Ho and lib with the opening Ia that the area of the gas entrance passage will be reduced by one-half. Further reduction can be obtained by producing a misalignment of the hole I lb with the opening Ia.

The actuator. I3. is mounted forreciprocation within the bearing cylinderll. The'shape of the actuator resembles that of a cup having an ex- The shank portion I5 of the actuator I3 extends through the bearing cylinder 6 and slides in a bearing surface provided by the hollow nut 9.

This shank is preferably provided with an enlarged diameter portion I5a adjacent the base of the cup shaped portion I4 thereby providing a shoulder I51). As has already been mentioned,

the actuator. I3 reciprocateswithin the bearing cylinder 6. Its forward movement is limited by the abutment of the base I40 of the cup shaped portion I4 against the end surface of the piston Illthus closing the gas passage Ilia. This abutting position as shown in Fig. 1 is the normal position of the actuator prior to discharge of a cartridge in the barrel B. The rearward movement of the actuator I3 brings the end of shank I5 into engagement with the breech operating rod I6. It should be understoodthat the showing of a rod I5 is merely a preferred embodiment and the end of the shank I5 of the actuator I3 may be readily adapted to cooperate with any portion of the breech operating mechanism upon which it is desired that an operating force be exerted. After striking the breech operating red It and moving it rearward, the movement of the actuator is limited by engagement of the shoulder I51) with the nut9 as shown in Fig. 2.

An alternative modification of the piston supporting arrangement is. shown in Figs. 6 and 7.

In this construction the shank II of the piston I0 is supported within the bracket 5 but the fit need not be as tight as that in Fig. 1. ton I0 is secured against any longitudinal movement by a pin 28 inserted transversely through the bracket 5 and an aligned slot 2Ia in piston shank II. A second slot 2Ibat right angles to, and intersecting slot 2Ia is also provided in piston shank II. When either theslot 2Ia or 2Ib is engaged by the pin 25, then radial gas passage III) or No is respectively aligned with the gas,

passage la in the supporting cylinder I. The corner normally produced by the intersection of slots 2Ia and 2Ib is rounded as'indicated at 22 (Fig. 7) to a radius equal to the perpendicular distance from the center of piston shank II to pin 20, thereby permitting rotation of the iston It; with pin 20 inserted, between the positions of respective alignment of slotsZIa and Zlb with pin 20. To yieldingly latch the piston I0 in either of these two positions aradial hole 23 is provided in piston shank II extending from the in tersection of slots 2Ia and 2Ib through the pi-ston shank II. A spring biased detent 24 is inserted in the hole 23 and .yieldingly engages pin 20. The latching action of detent 24 is readily overcome When a rotative force i applied to piston shank II as by insertion of a suitable tool in,

transverse slot 25 in the end of; shank II. Thus the-piston I0 may be rotated between two latched positions respectively aligning radial gas pas: sages IIb and Ho with passage Ia. V

In, operation, the firing of a cartridgein the barrel B generates gases behind the projectile, moving it out of the barrel. 1 A portion of these gases enter the porthole Cin the barrel and pass throughthe aligned openings Ia and the hole He or III) in piston I5, thence into the pas- The pissage Illa. The end of this piston passage is closed by the bottom surface I40 of the cup shaped portion M of the actuator l3. Thus only part of the area of surface Me is initially exposed to the gas pressure. The force of the gas pressure impinging against the surface He starts the actuator l3 moving rearwardly. Once movement is initiated, the entire area of the surface Me is subject to the force of the gases. Thus the maximum gas pressure force exerted on the actuator is reached in two steps.

The only escape path for the gases is by passage between the relatively small clearance between the maximum diameter portion iZ-a of the piston l and the interior surface Ma of the cup shaped portion l4. Thus a gas blast through this'small clearance is set up. This gas blast is continued along the entire bearing surface Ma since the slight tapered portion I of the piston l0 defining the gas passage does not immediately relieve the pressure. It should be noticed that the direction of the gas blast upon reaching the atmosphere is toward the muzzle end of the gun, and hence away from the operator. It is apparent that no appreciable accumulation of carbon or other deleterious substance deposited by the gas can occur on any of the surfaces Ma, Ma, and I211. Any substance deposited on these surface would be immediately blown off by force of the gas blast produced along these surfaces.

The energy imparted tothe actuator i3 by the high pressure gases is imparted to the breech operating rod i6 by the actuator striking it a hammer-like blow. The energy thus transmitted is utilized to unload the fired cartridge and load a new cartridge in the conventional manner of gas operated firearms. The actuator l3 may be returned to its initial position by the return of the breech operating rod IE to its battery position. If a clearance is provided between the end of the shank l5 and the end of the operating rod l6 such that the return of the rod IE to its battery position does not insure that the actuator l3 will be returned to its initial position, namely, with the surface Me abutting against the end of the piston I0, then a light cylindrical spring i! may be provided. This spring I? surrounds the shank l5 of the actuator l3 and operates between the nut 9 and the bottom of cup shaped portion M at I 4d.

When it is desired to fire cartridgeshaving difierent gas developing properties, the actuating mechanism may be compensated therefore by forced rotation of the discharge member ID within the bracket 5 to obtain an increase or decrease in the gas passage area in a manner that has already been described.

If it is ever desired to clean the parts of the actuating mechanism, it can be readily disassembled by removal of pin 1, hence permitting the removal of the nut 9. The actuator I3 may then be withdrawn from the bearing cylinder 6 and all bearing surfaces thereby exposed for easy cleaning.

I claim;

1. In a firearm having a barrel and a gas port therein, an actuating mechanism mounted on the firearm barrel in the vicinity of the gas port, said mechanism comprising a bracket extending radially from the barrel, said bracket having agas passage communicating with said gas port, a piston having an enlarged head and a shank, said shank being snugly mounted in said bracket but permitting forced rotational movement of said piston in said bracket, said head abutting said bracket, said head having a maximum diameter cylindrical portion, a movable cup-shaped cylinder having its interior walls slidably engaging the said cylindrical portion of said piston head with a relatively small clearance therebetween, an axial gas passage in said piston, said piston head having a decreasing diameter tapered portion adjacent said cylindrical portion and extending out of said cylinder, the taper of said tapered portion being selected to maintain a high velocity gas flow along the entire length of the interior walls of the cylinder, radial passages of different areas in said piston communicating between said bracket passage and said axial piston passage, and means on said piston arranged to receive a tool for rotating said piston in said bracket to vary the gas passage area by successive alignment of said radial gas passages with said bracket passage.

2. In a firearm having a barrel and a gas port therein, an actuating mechanism mounted on the firearm barrel in the vicinity of the gas port, said mechanism comprising a bracket extending radially from the barrel, said bracket having a gas passage communicating with said gas port, a piston having an enlarged head and a shank, said shank being rotatably mounted in said bracket, said head abutting said bracket, said head having a maximum diameter cylindrical portion, a movable cup-shaped cylinder having its interior walls slidably engaging the said cylindrical portion of said piston head with a relatively small clearance therebetween, an axial gas passage in said piston, said piston head having a decreasing diameter tapered portion adjacent said cylindrical portion and extending out of said cylinder, the taper of said tapered portion being selected to maintain a high velocity gas flow along the entire length of the interior walls of the cylinder, radial passages of difierent areas in said piston, each arranged to connect said bracket passage and said axial piston passage depending upon the rotational position of said piston in said bracket, means on said piston arranged to receive a tool to rotate said piston to vary the gas passage area by successive alignment of said radial gas passages with said bracket passage and a spring-pressed plunger mounted within the shank of said piston and cooperating with said bracket to latch said piston in each aligned position of said radial passages with said bracket passage.

J OHN C. GARAND. 

